456 [Assembly 



form is exceedingly combustiblej and is lighter than any othei 

 body known, and is generally found combined with water. 



Nitrogen chemically is opposed to combine with any other sub- 

 stance, and when compelled to do so, slight forces readily disunif]& 

 them. It is, nevertheless, always found in plants, and when they 

 die hastens their decay. 



Oxygen is the most important of all elements, constituting thp 

 chief part of the atmosphere, and all minerals and earths; it po^ 

 aesses neither smell nor taste, and is soluble to a certain degree in 

 water. 



The principal proportion of all vegetable tissues are compouncj? 

 oi oxygen, hydrogen and carbon. Fibre, starch, gum and sugar 

 are compounds of the elements of water and carbon, therefore a 

 fully developed plant requires matters containing carbon and ni- 

 trogen to aid their increasing organism, also the elements of water, 

 and finally a soil containing the inorganic substances necessary to 

 vegetable existence. The atmosphere affords great nourishment 

 |0 plants, its principal constituents are always found in the same 

 proportion. Combined with nitrogen it forms the chief constitu^ 

 ©nts of the atmosphere. 



Ammonia exists in the air, but has generally escaped the at- 

 tention of the chemist on account of the minute quantity, still WB 

 know it is there from the fact that rain water always contains it 

 ia solution. These are the constituents from which all plants ob- 

 tain their nourishment. From inorganic matters in the soil, plants 

 prepare that which nourishes them. Virgin eoils abound in ve- 

 getable substances admirably adapted for the growth of all plants, 

 as they consist in part of organic matters called humus or mould, 

 which is produced by the decay of vegetable matter, and must be 

 the proper food for living vegetables. It is readily dissolved in 

 alkalies, and partially in water. It is extracted in a soluble 

 form by the roots of plants, and in connection with carbon, feeds 

 their tissues; still many chemists declare that humus, as it exists 

 in the soil, is not nourishing to plants. It is so by presenting ^ 

 continual but slow source c^ carbonic acid gas. Wood, graij;^ 

 lifeay, corn, and many other plants produce carbon. 200 parts of 



